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AFPLICATIDI FIENDSOCT. I4. ISIS. 1 ,297,0405 v Patented Mar. 11,1919.

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mmmwm UNITED STATES PATENT OFFICE.

EDWARD A. TRAPP, DECEASED, LATE OF NEW YORK, N. Y., BY SUSANNA B. TRAPP, EXECUTBIX, 0F PHILADELPHIA, PENNSYLVANIA.

LENS.

Specification of Letters Patent.

Patented Mar. 11, 1919.

Application led October 14, 1916. Serial No 125,756.

To all whom t may concern.'

Be it known that EDWARD A. TRAPP, late a citizen of the United States and a resident of New York, in the county and State of New York, of whom I, SUSANNA B. TRAPP, of the city and county of Philadelphia and State of Pennsylvania, am the executrix, had invented in his lifetime certain new and useful Improvements in Lenses, of which the following is a specification.

The present device is a lens having the effect of a plano-parabolic lens, and is made in a very cheap and absolutely accurate form. It is based on the principle that if two parabolic cylinders are placed at right angles to each other with the right lines lying in the parabolic surface of one cylinder, lylng in planes cutting the other cylinder at right angles, a lens Will be formed which will have the characteristics of a lens having one side a plane surface, the other a stud the meridian curves of which are identical with the curves formed by the intersection of the cylindrical surface with a plane at right angles with the axis of its parabolic cylinder. The somewhat popular term parabolic cylinder may be defined as the surface generated by the movement of a parabola, so that its axis travels on a plane perpendicular to that in which the parabola is inscribed and the point of intersection of the parabola curve and its axis travels in a line perpendicular to the axis of the parabola at this point. I believe the enunciation of this principle is original to the decedent, as was also the recognition of the possibility of its application to the formation of lenses by employment of the curves of unequal radii, and hence the solution of the lens grinding problems hitherto preventing the making of lenses utilizing these curves. It is recognized that there are cases where the parabola is not the iinal form of curve in certain cases. Elliptical, hyperbolic or even other curves may be substituted, but in most instances the practical variance would be so small that the difference would be verbal rather than actual. The curve known as the Cartesian oval would seem the most frequent variant but this is, in its form and arc usable, so slightly variant from t-he arabola as to be practically identical W1th it. The various works on caustics may be consulted because where the loci of the refracted rays become each a single point for each corresponding point of the thing pictured, the curve in icated theoretically is the eX- actly right curve for a lens having the thing pictured at just that distance.

The thickness of the lens is that appropriate to the thickness of an ordinary planoconvex or plano-concave lens having the curved surface of the curves utilized, as said above, practically the parabola.

Figure 1 is a plan view of a magnifying lens. Fig. 2 is a side view of same. Fig. 3 is a section of same on line 'y-y of Fig. 1. Fig. 4 is a section on line .frof Fig. 1. Fig. 5 is a section on line Z-Z of Fig. 1. Fig. 6 is a section on line W--W of Fig. S. Fig. 7 is a diagram illustrating the curves and planes employed in generating the surfaces of the lenses. Fig. 8 is a plan view of a diminishing lens. Fig. 9 is a section on line U-U of Fig. 8 and Fig. 10 is a section on line V V of Fig. 8.

A plane passed through the axis of the lens and the line y-y will cut the face 30 on a right line and the face 31 in a parabola; a plane passed through the axis and line -m will cut the face 31 on a right line and the face 30 in a parabola. A plane passed through the axis and any line Z, Z, will cut the faces in paraboles having different values of their latus recta. As the cutting plane is revolved, on the axis of the lens, the parabola formed by its intersection with one face of the lens tends to become a straight line, and that formed by its intersection with the other tends to take the contour of the parabola shown in the Figs. 3 and fi. The thickness of the lens at any point at the same radial distance from the axis of the lens is the same. That is, if any point as 36 is taken on the line 33-34, the length of the line 35, 37, extending through this point to intersect with vthe surfaces of the lens at 35, 37 will be the same, no matter at what angle with the line .r--m the line Z-Z is taken. Similarly in the minus lens, a plane passed through the axis and line V, V, will cut the face 20 on a right line and the face 21 on a parabola, and the plane passed through U-U will cut the face 21 on a right line and face 2() on a parabola, while the plane passed through the line WWW which is any line in the quadrants between the line V-V and U-U, will intersect the faces 20 and 21 in parabolas having values of their latus recta different from that of the parabola shown in Fig. 9. The contour curves of these parabolas will vary and approach a straight line and a curve having the contour of the parabola shown in Fig. 9. The line 2627 intersecting the surfaces 20 and 21 passing through the point 28 in the line 29h-23 which is perpendicular to the axis 2&-25 of the lens, will always be of equal length whatever may be the in clination of the line W-W.

In Fig. 7 is shown a diagram of the generating curves and planes when the axes of the parabolas lie in the same straight line 5-6 and consequently coincides with the axis of the lens. The parabolas 9-10 and 11--12 are inscribed in the planes, 3 1 and 1 2 respectively. These planes make a right angle with each other. The axis of the parabola 9-10 moves in the plane, 1-2, the point 41 moving in the line 15-16 which is perpendicular to the line 5--6 at the point 41. The axis of the parabola 11-12 moves in the plane 3% and the point 40 in the perpendicular line 17, 18. The line 10--41 is the central thickness of a magnifying lens. The parabola 7-8 is inscribed in the plane 1 2, its axis moves in plane 3-4 and the point 42 moves in the line 13-14 perpendicular to the axis at this point. The length of the line 41, 42 measures the central thickness of the minus lens. The generation of other cylindrical forms other than parabolic would take place in the same way. The plus lens may be considered as the space included 'between the curved faces of two intersecting cylinders; the minus lens as a portion of the space between two non-intersecting cylinders, this space being disposed uniformly about a line forming a common axis of the generating curves of these cylinders.

Claims- 1. A lens with two curved faces having the characteristics of a parabolic lens, the curved surfaces of each of the faces being surfaces generated by the movement of the parabola in such direction that the axis of the parabola travels in a plane at right angles to the plane in which the parabola is inscribed and the oint of intersection of the axis of the para la with the curve of the parabola travels in a right line at right angles to the said plane in which the parabola is inscribed.

2. A lens with two curved faces having the characteristics of a parabolic lens of which the curved surfaces of each of these faces are surfaces generated by the movement of a parabola in such direction that the axis of the parabola travels in a plane at right angles to the plane in which the parabola is inscribed, and the point of intersection of the axis of the parabola with the curve of the parabola travels in a right line at right angles to the said plane in which the parabola is inscribed, the two faces being identical.

3. A lens having two curved faces and the characteristics of a parabolic lens of which the curved surfaces of each of the faces are surfaces generated by the movement of the parabola in such direction that the axis of the parabola travels in a plane at right an gles to the plane in which the parabola is inscribed and the point of intersection of the axis of the parabola with the curve of the parabola travels in a right line at right angles with the said plane in which the said parabola is inscribed, the two faces so arranged that the loci of the vertices of the generating parabolas lie in lines perpendicular to each other and that aforesaid planes generated by the movement of the axes of the parabolas intersect each other at right angles.

4. A lens with two curved faces having the characteristics of a parabolic lens of which the curved surfaces are surfaces generated by the movement of the parabola in such direction that the axis of the parabola travels in a plane at right angles to the plane in which the parabola is inscribed and the point of intersection of the axis of the parabola with the curve of the parabola travels in a right line at right angles with the said plane in which the parabola is inscribed, the two faces being identical and so arranged that the loci of the vertices of the generating parabolas lie in planes perpendicular to each other and that aforesaid planes generated by the movements of the axes of the parabolas intersect each other at right angles and the thickness of thelens at its axis is the theoretical length of the line measuring the thickness of the lens at that point.

5. A lens with two curved faces having the characteristics of a parabolic lens, of which the curved surfaces of each of the faces are surfaces generated by the movement of a parabola in such direction that the axis of the parabola travels in a plane at right angles to the plane in which the parabola is inscribed and the point of intersection at the axis of the parabola with the curve of the parabola travels in a right line at right angles with the plane in which the parabola is inscribed, the two faces being so arran ed that the loci of the vertices of the generatlng parabolas lie in lines perpendicular to each other, and that aforesaid planes generated by the movement of the axes of the parabolas intersect each other at right angles.

6. A convex lens with two curved faces, the curved surfaces of each of the faces being like surfaces, each generated by the movement of a convex curve, said curve having, and being symmetrical with reference to, an axis of symmetry parallel to the axis of the lens, the length of the radius vector, having its origin at the focus of the curve and generating each of the symmetrical portions of the curve being least when in coincidence with the axis of symmetry and this length increasing continuously, and being continuously in constant relation, with the angle the radius vector makes with this axis as said 5 vector revolves around the focus, the axis of each of the said curves in the generation of the surfaces traveling in a, plane at right angles to the plane in which such curve is inscribed, and said planes in which said axes travel being perpendicular to each other.

In testimony whereof I afiix my signature.

SUSANNA B. TRAPP, Eweewtm'w of Edwwrd A. Trapp, deceaefl.

Copies of this patent may be obtained for ve cents each, by addressing the Commissioner of Patents, Washington, D. C. 

